Mathematical modelling for biogas production
- Authors: Matheri, Anthony Njuguna
- Date: 2016
- Subjects: Sewage - Purification - Anaerobic treatment , Sewage - Purification - Mathematical models , Renewable energy sources , Biomass energy , Biogas
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213006 , uj:21066
- Description: Abstract: The main focus of this dissertation is the experimental, modelling and simulation of anaerobic digestion processes from pilot bio-digesters. For this purpose, biochemical kinetic models were utilized together with corresponding simulation software; DYNOCHEM. By application of the anaerobic digestion (AD), different parameters have been investigated and simulated including adjustments of the process model and corresponding modifications. To validate the process model, the modelled data was compared with experimental monitored laboratory results. Bio-chemical kinetics modelling was applied as a systematic tool in order to support the process design and optimization of a demonstration of the biogas processes which constitutes the main scientific framework and background of this dissertation. Monitored laboratory-scale biogas production data were used for parameter calibration in order to predict plant performance. The calibration focused on the influent characterization of both substrates and on selection of kinetic of the coefficients in order to generate a uniform set of parameters which are applicable for the simulation of codigestion. In this study, it was observed that the experiment work under laboratory scale using conventional bio-methane potential (BMP) analyzers under mesophilic optimum temperature of 35 oC and 37 oC, and pH of 7 for co-digestion of organic fraction of municipal solid waste (OFMSW) with cow dung and manure with grass clippings. The substrate characterization moisture content ranged from 60-95%, volatile content 55-95%, total solid 10-90% and carbon to nitrogen ratio 16-20 for manure and 5-15 for OFMSW. All trace elements concentration were below the threshold of 32 mg/l that leads to inhibition of micro-organisms activity. The rate of conversion increased with retention time. According to the findings, 54-62% of methane composition was evaluated. The kinetics constant evaluated ranged from 0.009-0.35 d-1 and coefficient of determination (R2) ranged from 0.9989-0.9998. The Michaelis-Menten and Monod models provided goodness of fit of 0.9997 with confidential level of 95%. The simulations confirmed that the rate of conversion increased as temperature increases and conversion of reactants increased with retention time, until an equilibrium state was reached. The AD process modelling using DYNOCHEM was successfully modified and implemented to account for unsteady operation which is generally the case of full-scale reactor by developed methodology. , M.Tech. (Chemical Engineering)
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- Authors: Matheri, Anthony Njuguna
- Date: 2016
- Subjects: Sewage - Purification - Anaerobic treatment , Sewage - Purification - Mathematical models , Renewable energy sources , Biomass energy , Biogas
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213006 , uj:21066
- Description: Abstract: The main focus of this dissertation is the experimental, modelling and simulation of anaerobic digestion processes from pilot bio-digesters. For this purpose, biochemical kinetic models were utilized together with corresponding simulation software; DYNOCHEM. By application of the anaerobic digestion (AD), different parameters have been investigated and simulated including adjustments of the process model and corresponding modifications. To validate the process model, the modelled data was compared with experimental monitored laboratory results. Bio-chemical kinetics modelling was applied as a systematic tool in order to support the process design and optimization of a demonstration of the biogas processes which constitutes the main scientific framework and background of this dissertation. Monitored laboratory-scale biogas production data were used for parameter calibration in order to predict plant performance. The calibration focused on the influent characterization of both substrates and on selection of kinetic of the coefficients in order to generate a uniform set of parameters which are applicable for the simulation of codigestion. In this study, it was observed that the experiment work under laboratory scale using conventional bio-methane potential (BMP) analyzers under mesophilic optimum temperature of 35 oC and 37 oC, and pH of 7 for co-digestion of organic fraction of municipal solid waste (OFMSW) with cow dung and manure with grass clippings. The substrate characterization moisture content ranged from 60-95%, volatile content 55-95%, total solid 10-90% and carbon to nitrogen ratio 16-20 for manure and 5-15 for OFMSW. All trace elements concentration were below the threshold of 32 mg/l that leads to inhibition of micro-organisms activity. The rate of conversion increased with retention time. According to the findings, 54-62% of methane composition was evaluated. The kinetics constant evaluated ranged from 0.009-0.35 d-1 and coefficient of determination (R2) ranged from 0.9989-0.9998. The Michaelis-Menten and Monod models provided goodness of fit of 0.9997 with confidential level of 95%. The simulations confirmed that the rate of conversion increased as temperature increases and conversion of reactants increased with retention time, until an equilibrium state was reached. The AD process modelling using DYNOCHEM was successfully modified and implemented to account for unsteady operation which is generally the case of full-scale reactor by developed methodology. , M.Tech. (Chemical Engineering)
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Studies on the improvement of biogas production from anaerobic digestion of animal wastes
- Authors: Sebola, Mmabyalwa Rebecca
- Date: 2015
- Subjects: Biogas , Sewage - Purification - Anaerobic treatment , Renewable energy sources , Biomass energy
- Language: English
- Type: Master’s Thesis
- Identifier: http://hdl.handle.net/10210/57296 , uj:16377
- Description: Abstract: The unsustainability of intensive reliance on fossil fuels and none-renewable resources as the main sources of energy, frequent rises in energy prices, the need for climate change mitigation and environmental protection have intensified the need for green energy. In this respect, green energy, in the form of biogas, has gained increased attention as a cost effective and environmentally cautious approach. This dissertation presents various studies aimed at improving the biogas production from anaerobic digestion of animal wastes. The experiments were conducted using the batch scale mesophilic tests. Characterisation studies (ultimate and proximate analysis) were conducted to identify key characteristics of the selected feedstocks. In addition, an economic assessment on the feasibility of anaerobic technology was conducted. The waste had average moisture content (MC) ranging from 7 – 34% and 70 – 81% for the dry and wet samples, respectively. The average volatile matter (VM) varied between 44 – 58% with the C/N for CD, CM, PM and SW being 26.20, 8.13, 17.64 and 8.57, respectively. Decreasing the particle size of the feedstock increased the amount of biogas significantly by increasing the total surface area of the material exposed to the anaerobic microbes. At optimal particle size (25μm), methane production was 3 – 30 % higher as compared to that of 100μm and above. Highest methane yields were achieved from CD to CM, PM and SW at ratio of 1:1:1:1. At optimum temperature (40˚C), the highest methane yield (62% CH4/ d) was obtained on Day 6. Adding 50% VS resulted in more methane yields (64% CH4/d) than 30 and 40%. An introduction of 40% recycled liquid and 60% fresh water to the digester gave the best performance, with 73% CH4/d of biogas produced within 5 days. Soaking the feedstock prior digestion improved both the methane and biogas yields and stability of the process. An economic evaluation over a period of 5 years with 8 hours daily operation and a breakeven of 1.5 years was assessed. The proposed model has debt repayments of R 2,478,551 with the total revenue from years 2 – 5 being R 2,360,800, R 2,930,158, R... , M.Tech. (Chemical Engineering)
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- Authors: Sebola, Mmabyalwa Rebecca
- Date: 2015
- Subjects: Biogas , Sewage - Purification - Anaerobic treatment , Renewable energy sources , Biomass energy
- Language: English
- Type: Master’s Thesis
- Identifier: http://hdl.handle.net/10210/57296 , uj:16377
- Description: Abstract: The unsustainability of intensive reliance on fossil fuels and none-renewable resources as the main sources of energy, frequent rises in energy prices, the need for climate change mitigation and environmental protection have intensified the need for green energy. In this respect, green energy, in the form of biogas, has gained increased attention as a cost effective and environmentally cautious approach. This dissertation presents various studies aimed at improving the biogas production from anaerobic digestion of animal wastes. The experiments were conducted using the batch scale mesophilic tests. Characterisation studies (ultimate and proximate analysis) were conducted to identify key characteristics of the selected feedstocks. In addition, an economic assessment on the feasibility of anaerobic technology was conducted. The waste had average moisture content (MC) ranging from 7 – 34% and 70 – 81% for the dry and wet samples, respectively. The average volatile matter (VM) varied between 44 – 58% with the C/N for CD, CM, PM and SW being 26.20, 8.13, 17.64 and 8.57, respectively. Decreasing the particle size of the feedstock increased the amount of biogas significantly by increasing the total surface area of the material exposed to the anaerobic microbes. At optimal particle size (25μm), methane production was 3 – 30 % higher as compared to that of 100μm and above. Highest methane yields were achieved from CD to CM, PM and SW at ratio of 1:1:1:1. At optimum temperature (40˚C), the highest methane yield (62% CH4/ d) was obtained on Day 6. Adding 50% VS resulted in more methane yields (64% CH4/d) than 30 and 40%. An introduction of 40% recycled liquid and 60% fresh water to the digester gave the best performance, with 73% CH4/d of biogas produced within 5 days. Soaking the feedstock prior digestion improved both the methane and biogas yields and stability of the process. An economic evaluation over a period of 5 years with 8 hours daily operation and a breakeven of 1.5 years was assessed. The proposed model has debt repayments of R 2,478,551 with the total revenue from years 2 – 5 being R 2,360,800, R 2,930,158, R... , M.Tech. (Chemical Engineering)
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